The script we use for pulling translations from Transifex did only update already existing locale files. I updated our script so that it also adds missing locale files.
https://github.com/discourse/discourse/commit/74a855b08d38681d00f4c37e1e84dd96a7e36a35
And I updated all translations and added a few missing locale files.
https://github.com/discourse/discourse/commit/de19c8e70cf54813bfda2607edf6f230e535e673
@karasardelis Thanks for your PRs. I closed them since they had the wrong language in the file header, but I added the Greek locale files in my commit.